Is my MFT knackered or just plain stupid?!

[DNS1]

Was testing earlier and my measured R1+R2 values decreasing the further I was from the DB...

Turns out I'd nulled with my 30m wander lead earlier, but even though the machine had been switched off it hadn't reset. It was taking every reading and subtracting the 0.50 ohms measured on the long lead. No errors thrown up by the machine, so it was displaying a 0.15 ohm continuity as 0.35 (in reality it must have read -0.35 but my MFT doesn't display a negative symbol...

Is this normal?!

It's a Metrel MI3000...

 

[pete555]

Was testing earlier and my measured R1+R2 values decreasing the further I was from the DB...

Turns out I'd nulled with my 30m wander lead earlier, but even though the machine had been switched off it hadn't reset. It was taking every reading and subtracting the 0.50 ohms measured on the long lead. No errors thrown up by the machine, so it was displaying a 0.15 ohm continuity as 0.35 (in reality it must have read -0.35 but my MFT doesn't display a negative symbol...

Is this normal?!

It's a Metrel MI3000...

there by lies the problem throw it away and buy a fluke that way you get proper results every time

 

[Resu]

there by lies the problem throw it away and buy a fluke that way you get proper results every time

Ha, no! We had a problem with two fluke MFTs, switched to Megger, no problems since.

 

[dan86]

lol! I ain't gonna join in on this one, but Pete and I both know each others views on Fluke vs Megger!!!

 

[telectrix]

the best thing about flukes is that you can use the case as a sarnie box and/or a seat.

 

[DNS1]

Not going to be drawn in to the Fluke vs Megger vs Metrel vs anything else row!

For everyone's info, I bought the Metrel as the current version of the "industry standard" Megger didn't work properly and kept tripping RCDs!

 

[Richard Burns]

Was testing earlier and my measured R1+R2 values decreasing the further I was from the DB...

Turns out I'd nulled with my 30m wander lead earlier, but even though the machine had been switched off it hadn't reset. It was taking every reading and subtracting the 0.50 ohms measured on the long lead. No errors thrown up by the machine, so it was displaying a 0.15 ohm continuity as 0.35 (in reality it must have read -0.35 but my MFT doesn't display a negative symbol...

Is this normal?!

It's a Metrel MI3000...

I would have thought this was normal, the MFT will remember the settings you have even if you have switched off.
other wise if you are doing lots of testing on a long lead you would need to have the MFT on all the time as you wandered round the building. Just need to remember to null every time you change.

 

[brman]

I would have thought this was normal, the MFT will remember the settings you have even if you have switched off.
other wise if you are doing lots of testing on a long lead you would need to have the MFT on all the time as you wandered round the building. Just need to remember to null every time you change.

But to display a negative result as positive sounds a bit dodgy? Easy enough to test though - null with your long lead then remove the long lead and do a zero check. What do you get?

Anyway, my fluke is not much better, anything negative gets displayed as zero. Which is why I have a 1 ohm resistor taped to it which I can use as a sanity check when I need to.

 

[Octopus]

I have a Metrel, and when the R1+R2 readings start "wandering" I know its time to buy a new set of leads.

 

[Amp David]

Not going to be drawn in to the Fluke vs Megger vs Metrel vs anything else row!

For everyone's info, I bought the Metrel as the current version of the "industry standard" Megger didn't work properly and kept tripping RCDs!

And also doesn't display a negative symbol

 

[rocker]

Um.... am I reading this right? You zeroed your meter to your r2 lead, didn't re-zero it and then wondered why you got high readings? Just re-zero it with your normal probes and bob's your auntie's live-in lover.

 

[DNS1]

Um.... am I reading this right? You zeroed your meter to your r2 lead, didn't re-zero it and then wondered why you got high readings? Just re-zero it with your normal probes and bob's your auntie's live-in lover.

That's pretty much it to be honest!

I wasn't expecting my meter to measure a negative reading on a circuit and display it as a high positive reading!

 

[rocker]

Ahh I see. Yea, that is weird. I think mine just says 0.00